| abstract |
The process for producing polyesters, and in particular, polyethylene terephthalate (PET) which includes the use of antimony catalyst that is acidic phosphorus additive involves the addition of the catalyst prior to or together with the additive. Moreover, the amount of additive is selected so as to provide a resin that is at least substantially free of non-acidic inorganic compounds such as antimony phosphate which can be formed by the reaction of the catalyst with the additive. The process preferably includes an esterification step, a prepolymer step, and a polymerization step with the antimony catalyst being added prior to, during, or after, the esterification step while the phosphorus-containing additive is introduced prior to or during the prepolymer stage. Polyesters having low levels of elemental phosphorus are also disclosed. |